𝐁𝐚𝐜𝐭𝐞𝐫𝐲

The battery in a car is a rechargeable. It supplies power (electric energy) to the car. Normally this battery is used to help provide power to start the car and then it is used only when extra power is needed. The car battery alone is can't supply power to all the electrical systems. The alternator does this.
The battery is connected to your lights and car accessories, like the radio, when the engine is off. Leaving the lights or radio on too long will drain the battery. If you don't leave it on too long your car's battery will recharge during about a 30 minute drive.
A completely or partially (below 10.5 Volts) drained battery is not good. It causes damage to the battery. It is advisable to turn off car lights and accessories soon after the car engine has stopped.